1. Field of the Invention
This invention relates in general to a kind of power management and control circuit of a computer system, and more specifically relates to a wake-up control circuit used to wake a personal computer or work station when the micro processor is in standby mode. The invention further specifically relates to a wake-up control circuit to wake up a computer by using the peripherals rather than the panel switch.
2. Description of Related Art
The Macintosh personal computer manufactured by Apple Computer Inc. of Cupertino, Calif., uses specified keys on the keyboard to turn the computer on or off. The method is very convenient.
On the other hand, Intel Corporation of Santa Clara, Calif., provides a specification for a personal computer, called The ATX specification. In the ATX specification, power is no longer controlled by a mechanical switch. The ATX specification manages and controls the power of the whole computer system by a control chipset within the computer. This is a soft power control concept, which uses various methods to turn the computer on or off and is not limited to mechanically switching the power on or off.
As an example of ATX specification version 2.01, the standby power 5VSB is DC 5V, which provides a maximum output current of 0.7A in order to drive the basic power management circuit of a computer system in the power-off state. The management circuit can be set up to process various convenient functions. For example, the system can be set up in advance so that the system can be activated at a predetermined time at night.
Intel, Microsoft and Toshiba, which define different standby modes between operation and power-off of a computer system, provide a specification of an advanced configuration and power interface (ACPI). The computer decides an appropriate standby mode for saving power according to the amount of tasks the computer has. In accordance with the amount of power saving, from small to large, there are four standby modes, which are S.sub.1 :stop CPU clock, S2:suspend to RAM,S3:suspend to disk and S4: soft off. When the computer is in the mode of suspending to RAM, the S2 mode, the clock pulses on the mainboard other than the real-time clock are all suspended; therefore, all tasks are stopped because no clocks are inputted to the CPU and other circuits. When the user tries to wake up the computer, the user cannot wake up the computer system by a keyboard controller or infrared controller (or serial port) because all of the peripherals are suspended. Under these conditions, the user has to push a button to inform the computer to resume operations. Accordingly, the conventional computer system can not be woken up by its peripherals.